southern nevada recycles 100% of its wastewater. so for every gallon we put back in the colorado, we can take an additional gallon out, or we send it to reuse facilities. and we deliver it to golf courses and parks and other outside applications. man: water's about a third of our budget. that's a lot of money. the lake right over here, 24 hours ago that was in somebody's house. it's been through a treatment plant. and now it's in our lake and we're watering with it. narrator: these reuse and conservation techniques enable las vegas to exist in the desert. another important form of conservation is preventing leaks. man: every drop counts. all water systems have what they call an efficiency rating. so if you were to measure the water that goes into your system and compare it to the water that goes out, how much is unaccounted for? most states have a goal of 10%. ours is at only 5.5% right now. and we have plans to lower that to 4%. man: we actually have our entire distribution system mapped out in a computerized or electronic format.